USGS Field Activities 12BHM01, 12BHM02, 12BHM03, 12BHM04 and 12BHM05 on the West Florida Shelf, in February, April, May, June and August 2012 By Lisa L. Robbins,1 Paul O. Knorr,1 Kendra L. Daly,2 and Kira E. Barrera,1. 1) U.S. Geological Survey, St. Petersburg, FL 33701. 2) University of South Florida, College of Marine Science, St. Petersburg, FL 33701 To access the information contained on this disc, use a Web browser to open the file index.html. System Requirements This Web page or disk is readable on any computing platform with a modern Web browser. Downloadable content can be viewed with a portable document reader (PDF), a text editor, spreadsheet software, and Geographic Information System (GIS) software. If you cannot fully access the information on this page, please contact USGS Information Services at infoservices@usgs.gov or 1-888-ASK-USGS. Introduction Atmospheric carbon dioxide (CO2) is absorbed by the ocean’s surface where it combines with seawater to form a weak, naturally occurring acid called carbonic acid (H2CO3). Increasing carbon dioxide in the atmosphere results in the absorption of more CO2 by the ocean and, therefore, increases in the acidity of seawater. This process, known as ocean acidification, has the potential to elicit change in ecosystems and organisms by disrupting biological processes. For example, ocean acidification is a problem for marine organisms such as corals, foraminifera, and algae that precipitate calcium carbonate to form their skeletons and shells (Kleypas and others, 2006). The effects are related to corresponding changes in the carbonate saturation state (Ω), where Ω is the ratio of the ion concentration product (Ca2+ x CO32-) to the stoichiometric aragonite solubility product (K*sp) (Langdon and Atkinson, 2005). Because pH and CO32- are strongly interdependent through the inorganic carbon system, the decrease in pH will cause a proportionally greater decrease in CO32-. Globally, ocean acidification is occurring faster than at any time in the last 300 million years (Broeker and others, 1979). Recent evidence indicates that individual oceans are responding at different rates, depending on physical and biological processes. For example, in the Arctic Ocean the rate of saturation state decrease was 2.1 percent per year between 1997 and 2010 (Robbins and others, 2013) in an area as large as Montana, largely because of increases in the melt of ice versus the average rate observed for the Pacific Ocean (0.36 percent per year) (Feely and others, 2012). Unfortunately, comparative data sets over multiyear timeframes are not often available because time series baseline carbon information has not been collected in many oceans. Data are needed in subtropical latitudes where carbonate saturation states are already naturally low and fluctuate seasonally. These data will help construct a baseline for the assessment of future changes. As part of the U.S. Geological Survey (USGS) Coastal and Marine Geology Program project "Response of Florida Shelf Ecosystems to Climate Change" and in partnership with Kendra Daly, University of South Florida (USF), data on surface ocean carbonate chemistry were collected on five cruises along transects on the shallow inner west Florida shelf and northern Gulf of Mexico in 2012. Data from 2011 cruises were also published (Robbins and others, 2013). The data collected will allow the USGS, National Oceanic and Atmospheric Administration (NOAA), and USF scientists to map variations in ocean chemistry including carbonate saturation states along designated tracks. The USGS is also partnering with NOAA and the National Aeronautics and Space Administration (NASA) to model air-sea flux as part of a Gulf of Mexico Carbon Synthesis project lead by NASA. Project Summary During February, April, May, June and August of 2012, the USGS and USF conducted geochemical surveys on the west Florida Shelf to investigate the effects of climate change on ocean acidification within the northern Gulf of Mexico, specifically, the effect of ocean acidification on marine organisms and habitats. The cruises were conducted February 15 to 24 (12BHM01), April 24 to 29 (12BHM02), May 8 to 17 (12BHM03), June 29 to July 1 (12BHM04) and August 2 to 12 (12BHM05). To view each cruise's survey lines, please see the Trackline page. Cruises took place aboard the Research Vessels (R/V) Weatherbird II and Bellows, ships of opportunity led by Kendra Daly, USF, which departed from and returned to St. Petersburg, Florida. Samples were collected from the surface and the water column and analyzed in the lab for pH, dissolved inorganic carbon (DIC) or total carbon dioxide (TCO2), and total alkalinity (TA). Lab analysis was augmented with a continuous flow-through system, referred to as sonde data, with a conductivity-temperature-depth (CTD) sensor, which also recorded salinity and pH. Corroborating the USGS data are the vertical CTD profiles, referred to as station samples, collected by USF. The CTD casts measured continuous vertical profiles of oxygen, chlorophyll fluorescence, and optical backscatter. Discrete samples for nutrients, chlorophyll, and particulate organic carbon/nitrogen were also collected during the CTD casts. Two autonomous flow-through (AFT) instruments recorded pH and CO2, referred to as AFT data, every 3 to 5 minutes on each cruise. Disc Organization This report is divided into six sections: Abbreviations, Disc Contents, Methods, Cruise Data, Federal Geographic Data Committee (FGDC) Metadata, and Trackline. Links at the top and bottom of each page provide access to these sections. This report contains links to the USGS, collaborators, and other available resources if access to the Internet is available while viewing these documents. Geographic information system (GIS) files, HyperText Markup Language (HTML) files, and images used to produce the Web pages are also included in this report. The Disc Contents page contains a listing with locations and links to all files and folders contained on this disc.